1. Field of the Invention
The apparatus disclosed herein relates to mechanical broom sweepers and more particularly to such sweepers which have the capability of sweeping over irregularities on the swept surface while maintaining sweeping contact with the surface.
2. Description of the Prior Art
A power driven sweeping machine is disclosed in U.S. Pat. No. 2,448,328, issued to A. Russell, in which a machine body portion contains a forwardly located debris receiving bin. The body portion has a forwardly located towing arm attached thereto and a set of rear supporting wheels so that it may be towed behind a suitable tractor. Under the body portion a brush housing is supported on a forwardly located pivot and a number of rearwardly located depending support arms. The support arms include coil springs which absorb the shocks imparted to the brush housing. A series of sprocket chains are coupled between the rear supporting wheels and a pair of sweeping brushes which are mounted on shafts supported between the side walls of the brush housing. When the body portion is towed in a forward direction, the rotation of the rear support wheels causes the sweeping brushes to rotate and to thereby sweep an underlying surface. One of the brushes clears debris off of the underlying surface and elevates the debris to the second brush which in turn sweeps the debris toward the debris receiving bin within the body portion.
A street sweeper is disclosed in U.S. Pat. No. 982,570, issued to C. C. Brooks, which sweeper includes a casing supported on members depending from a framework. The depending members include coil springs which allow the casing to move in a vertical direction relative to the framework. A number of brushes are driven by a chain drive which is coupled to the drive wheels on the framework of the sweeper. The brushes are mounted within the casing on shafts which extend between journals disposed in the side walls of the casing. The casing and brush assembly may move vertically against the yielding coil springs to compensate for uneven characteristics in the underlying surface being swept.
U.S. Pat. No. 1,286,481, issued to N. C. Woodin, discloses a broom support for a street sweeper wherein a broom having an overlying hood is driven through a chain drive. The broom is mounted on a shaft extending between two broom support arms. The broom is movable in a vertical direction as the support arms are pivoted about a transverse pivot shaft connecting the broom's support arms together behind the broom. A spring is provided which is positioned above the broom and the hood and is coupled to the ends of the broom shaft for the purpose of absorbing shock imposed upon the system due to sudden downward broom movement.
A sweeping machine is disclosed in the O. F. Presbrey U.S. Pat. No. 1,904,881, in which a rotary broom is mounted forward of a mobile vehicle and is supported by a cable system attached to the vehicle. Raising and lowering of the broom is accomplished by manipulation of the cable system and the broom is said to be in a freely floating condition in front of the vehicle as the supporting cable for the broom is maintained in a taut condition at all times during operation by a pair of coiled tension springs. The entire broom assembly in the Presbrey patent may move vertically, or one end may move vertically independent of the other end so that the broom follows the topography of the underlying surface being swept.
Another sweeping machine is disclosed in the J. R. Royer U.S. Pat. No. 2,156,065. A sweeping machine arranged to be towed by another vehicle is configured so that two rotary brooms are mounted underneath the machine, each of which is capable of independent vertical motion relative to the framework of the machine. A motor is provided for driving the two brooms through appropriate chain and sprocket linkage. Dirt deflectors are mounted adjacent to the upper periphery of the brooms and move vertically therewith. A coiled tension spring is coupled between the framework and the structure supporting the brooms so that the brooms are suspended resiliently beneath the frame and may therefore ride upwardly and over projections on the surface being swept.
Another surface sweeper is disclosed in U.S. Pat. No. 4,007,026, issued to A. F. Groh. An industrial sweeper contains a hopper supported on the sweeper framework. A dust filter configured as a number of rows of cartridges having pleated paper filter elements is located within the hopper between a dust laden air portion of the hopper and a filtered air portion. The filters are cyclically cleaned by the application of reverse air jet pulses. The cleaning is performed in only a portion of the filters at any one time. A broom chamber is rigidly affixed to the framework containing a rotating broom which is disposed to engage an underlying surface to be swept. The broom is movable vertically within the broom chamber over a limited distance and serves to sweep debris and dust from the underlying surface toward an elevator paddle which urges the dust and debris through aligned apertures in the broom chamber and the hopper so that the dust and debris is collected within the hopper. A blower exhausts air from the filtered air portion of the hopper, thereby drawing an airflow along a path from the underlying surface into the broom chamber, into the dust laden air portion of the hopper, to the filter and the filtered air portion of the hopper and to the atmosphere. While the Groh device will accommodate small irregularities in the surface being swept, it will not sweep continuously and afford good dust control when encountering large irregularities in the underlying surface, such as parking lot speed bumps.